ARM64: Fix SHR logic error.

The `right == 0` checks only worked for `0 <= right < 32`. This patch
replaces the checks with simple tests for negative results.

The attached test can detect this error, but the test relies on a broken
flag (--noopt-safe-uint32-operations), so it is skipped for now. See
issue 3487 for details.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/487913005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23243 ce2b1a6d-e550-0410-aec6-3dcde31c8c00